Drying Characteristics of Lemon By-product (Citrus limon. v. lunari): Effects of Drying Modes on Quality Attributes Kinetics

• Published in: Waste and biomass valorization 2020, Vol.11 (1), p.303-322
• Main Authors: Ghanem, Nesrine, Mihoubi, Daoued, Bonazzi, Catherine, Kechaou, Nabil, Boudhrioua, Nourhene
• Format: Article
• Language: English
• Subjects: Air drying; Citrus fruits; Citrus limon; Color; Dehydration; Drying; Drying oils; Engineering; Engineering Sciences; Environment; Environmental Engineering/Biotechnology; Flavonoids; Industrial Pollution Prevention; Infrared heating; Kinetics; Lemons; Life Sciences; Original Paper; Phenols; Polynomials; Quality management; Renewable and Green Energy; Retention; Retention capacity; Waste Management/Waste Technology
• ISSN: 1877-2641; 1877-265X
• DOI: 10.1007/s12649-018-0381-z

The aim of this work is to establish a comparative investigation of the effect of different drying processes: microwave dehydration (100–600 W), air drying (40–60 °C) and infrared drying (40–60 °C) on drying kinetics and on the main quality attributes (color, total phenols and flavonoids contents, water and oil retention capacities) kinetics’ of lemon ( Citrus limon . v. lunari) peels. The experimental drying kinetics’ of lemon peels were fitted to nine thin layer drying models. The Midilli and Kucuk model showed a better fit to experimental drying data for the three drying processes. Microwave drying at 450W preserved the maximum phenols (1.855 ± 0.016 g CAE/100 g DM) and flavonoids (0.802 ± 0.072 g RE/100 g DM) contents respectively. An increase of phenol content was noticed after 9, 13 and 14 min of microwave drying at 600, 450 and 300 W and after 156, 102 and 54 min of infrared drying at 40, 50 and 60 °C. A first-order kinetic model adequately fitted, at the beginning of drying processes, the change of total phenols and flavonoids contents. Total color difference ( ΔE) increased progressively with increasing drying time and temperature or microwave power level. ΔE showed a zero-order model whatever the applied drying process. Water retention capacity ( WRC ) of dried lemon peels decreased during drying processes. However, infrared and microwave drying increased the oil retention capacity ( ORC ) of lemon peels. The WRC and ORC followed first-order kinetics during air drying and a second order polynomial model during microwave and infrared drying processes.